David Cameron today returns to one of the Conservatives' core issues, school discipline, to help reassure party members that he is as concerned with the domestic agenda as foreign policy. In a speech to the rightwing thinktank Policy Exchange, the Tory leader will take advantage of the late cancellation of a trip to Pakistan to explain the Conservatives' plans to give headteachers more control over expulsions, and to argue that discipline is the foundation of all successful schools.

Ed Balls, the children's secretary, has promised to make school discipline one of his priorities too and says school inspectors must "raise the bar" on what is acceptable behaviour inside the classroom.

Yesterday, Mr Cameron endorsed a new party report on the education of pupils with special needs which called for reform of the statementing system which could lead to it being taken out of local authority control.

Mr Cameron's aides insist the postponement of the Pakistan trip was logistical rather than political, and he will visit elsewhere in the region shortly.

But a long-planned trip to Rwanda at the height of the floods last week was criticised by some party members and Tory-supporting newspapers. The Conservative leader yesterday received two more broadsides from inside the party, suggesting that weekend appeals to rally behind him will be difficult to enforce.

The most wounding was from Lord Saatchi, the advertising pioneer and former Tory chairman, who told Mr Cameron to concentrate on the economy. "Nicey-nicey has not led to more affection for the Conservative party. According to the prevailing theory, this is a 'brand image' problem ... unfortunately ... 'nastiness' is irrelevant to electoral outcomes," Lord Saatchi wrote in the Evening Standard in London. "Nothing will happen until the Conservative party has something compelling to say about the subject that matters - economics."

Such criticism adds to the pressure on George Osborne, the shadow chancellor, who some senior Tories believe should have been moved out of that post to concentrate on his role of general election coordinator. Some shadow cabinet members believe Mr Osborne's relative success against Mr Brown across the dispatch box made senior Tories complacent about the impact of the Brown leadership.

The other advice for Mr Cameron yesterday came from Edward Leigh, MP for Gainsborough, chairman of the public accounts committee, and habitual critic of the leader. "We do need to talk more about immigration, low taxes and Europe, both to enthuse our activists and because whilst old Labour policies were bad for the country, old Conservative ones, such as lower taxation, are the reality in the world's most successful, dynamic economies," Mr Leigh wrote in Parliamentary Monitor magazine. "Our David in his heart of hearts is a High Tory. He just needs to show it more, as well as showing that he cares about the environment and the poor. Liberalism doesn't win elections."

There was also bad news in two polls. One for the Times put Mr Cameron behind Mr Brown in almost all measures and Labour ahead on 39% (up two points on a similar Populus poll last month), the Conservatives on 33% (down one) and the Liberal Democrats on 15% (down three). A CommunicateResearch survey for the Independent put Labour on 37% (up five points on a similar poll last month), the Conservatives on 34% (down three) and the Liberal Democrats 16% (down two).